Process for the production of iron sponge



May 2l, 1929 s. E. SIEURIN 1,714,280 l PROCESS FOR THE PRODUCTION 0FIRON SPONGE med nec. 17, 1927 @noo l INYENM( SVEN EMIL SEUR/N PatentedMay 2l, y1929.

UNITED STATESI l 1,714,280 PATENT oFFlcE.

SVEN BIEURIN, OF HOGANAS, SWEDEN.

PROCESS FOB THE PRODUCTION OF IRON SPONGE.

Applicationlled December 17l 1927, Serial N0.,240,908, and SwedenJanuary 26, 1926.

v It has been proposed toproduce` metals,'by"

first embedding ore in the shape of bricks, pieces or layers orpulverized ore 1n a solld reducing agent` (suitably carbon), heatingwithout any supply of air or any-other gas to a temperature necessaryfor the reduction but under that for melting, and finally by separatingthe reduced metal at the end of the reducing process from the'remainingreducing a et.

his process, ywhich is especially suita le for the' production of ironsponge, hasl the disadvantage of affording some diiiiculties in theproduotion'of an ironsponge which 1s suliciently free from su1phur,s1ncethe process affords several possibilities for the combination withsulphur.

The ore itself may be sulphurous or the reducing agents'may containsulphur, which combines with the ore during the heating rocess. Toovercome the disadvantage of the own methods, the reducing agents maybel mixed with the oxides ofthe common metals of the alkaline earths,calclum and magnesium, which then combine with the sulphur in the ore orthe carbonaceous reducing agent to form the sulphides of the commonmetals of the alkaline earths, 'the calcium and magnesium having beendecomposed from the line and'magnesia Aduring the process.

During the heating, forming part of thereducin process, a decompositionof the pyrites and ot er sulphurous combinations contained in thereducing agents (usually coal or coke) takes place at a comparativelylow temperature (400-700 (l), whereby the sulphur or volatilecombinations of same are set free and the sulphur immediately combineswith the iron ore, because the lime stone and magnesia which may havebeen added to the reducing agents havenot been decomposed and are notable .to combine with sulphur at the said low7 temperature. It has alsobeen found that on account of these circumstances an ore, heated to 500C. may contain a percentage of sul hur of several tenths.

ttempts to reduce the percentage of sulphur in the product (ironsponge), obtained cooling of the charge contributes to a rapid decreasein the excess of carbon,that may be present. Even if a comparativelylarge excess of reducing agents `(carbon) is resent in the ash, adecomposition of the su phides of calcium and magnesio., which'mayhavebeen formed, gradually takes place.

It is also quite obvious that the time required'forthe process and thetemperatures to which the ore must'be raised depend upon the thicknessofthe layersof pulverized ore.

In the accompanying drawing a dia ram is shown, illustrating how thesulphuriis absorbed by the ore and further the desulphurizing during thereducing process of the'iiron sponge obtained as well as the laterrepeated a.

sorption of sulphur in the iron sponge. The lowest oint ofthe curve ofthe percentage of sulp ur designates the time when the reduction isfinished. The dia ram illustrates not only the variations in t epercentage of sul hui` during the reducing process but also t evariations of the temperature duringthat process. -It exemplifies areducf ing process carried out during very unfavourable conditions, viz,a process in which the cooling of the reduced product has taken placevery slowly. From the above it will be evidentv that. the sulphur isagain combined with the iron sponge and this undesirable combinationtakes place more rapidl the slower the sponge is cooled. This resu tassumes that a sufficient quantity of reducing agents (carbon) is notpresent in the ash at the end of the reducing process.

In order to obtain a product which is as vfree as possible from sulphurthe cooling must take place at a rate which variesI inversely as theexcess of carbon present. In other words if there is a small'excess ofcarbon in the ash the cooling must be rapidly effected and if the excessof carbon present is large the mass may be cooled at a lower rate. lThese two facts, the excess of reducing agents in the ash and therapidity ofthe A.

cooling corresponding inversely to said excess are of fundamentalimportance in the production of iron sponge according tor the presentinvention.

Having now particularly described thenature of my invention and themanner of its operation, what I claim is:

A, process for the production .of iron sponge complrising embeddingpulverized iron ore in t e desired shape in a carbonaceous reducingagent, heating the mass in the absence of any gas to a temperature lessthan the melting point of the iron ore but suicient for the reductionthereof and finally cooling thc mass, characterized by the presence ofthe oxides of the common metals of the alkaline earths, the addition ofcarbonaceous reducing agent to constitute an excess over that requiredfor the reduction, and cooling the product, said cooling beingaccel#erated so that the sulphide formed in the charge will not be decomposedand will not liberate the combined sulphur, thereby pre venting theundesirable absorption t ereof by the iron sponge.

In testimony whereof I aiiix my signature.

SVEN EMIL SIEURIN.

